Metal-free N–S co-doped electrode for electrochemical CO₂ reduction to HCOOH

This paper presents metal-free N–S co-doped catalysts that synthesize in the presence of different S sources such as thiourea and polythiophene (Ptyf). The composition, morphology, and structure of the obtained sample are measured by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), UV–vis spectroscopy, Fourier transform ınfrared-attenuated total reflection spectroscopy (FTIR-ATR), and X-ray photoelectron spectroscopy (XPS). Although the characterization measurements showed that the fabricated catalysts had a similar elemental composition, the polythiophene-based catalysts retained their polymer properties such as active surface area, conductivity, and conjugated chains. This result enhances the adsorption of CO₂ to the catalyst surface and promotes the reduction of CO₂ effectively. The only product is HCOOH with a faradaic efficiency of 84% which was achieved on P-N/S₂-rGO (P: pyrolysis) at -0.6 V (Ag/AgCl).